1. Field of the Invention
The invention relates to a power line communication system in which power lines are used as communication media.
2. Description of the Related Art
Power line communication (PLC) technology uses existing power lines, such as an in-building power line network or in-car power supply lines, for transmitting digital processed data or information. In a case where an existing in-building power line network is used to transmit signals, since there is a lot of electrical equipment connected to the in-building power line network, noise usually occurs and interferes with power line communication when the electrical equipment connected to the in-building power line network is turned-on, turned-off, plugged-in or plugged-off, thereby causing problems such as an interruption in power line communication.
FIG. 1 is a block diagram of a known power line communication system in which an in-building power line network is used to transmit signals. The power line communication system comprises a distribution transformer 100, a power distribution panel 110 at a home user end, live wires L1 and L2, a neutral wire N, a ground wire G and power line communication devices A and B. The distribution transformer 100, such as a pole-mount transformer mounted on a utility pole, steps down voltage provided by a power supplier to an appropriate voltage used by the home user. The power distribution panel 110 is connected to the power line network of the home user and provides power to the power line network. For example, the power distribution panel 110 provides 110-volt single phase AC power to the live wires L1 and L2 and switches and controls the distribution of power. For the sake of brevity, FIG. 1 only illustrates a part of the power line network. Conventionally, data is transmitted from the power line communication device A to the power line communication device B through a path including the live wire L1, the power distribution panel 110 and the live wire L2, as shown by the path P in FIG. 1. However, when serious interference occurs on the live wire L1 due to noise 120, such as a turning-on, turning-off, plugging-in or plugging-off of electrical equipment, the power line communication may be interrupted.
In order to solve problems caused by noise interference, some technologies may use filters configured in the power line communication system to filter noise so as to reduce noise interference.